I'm trying to build an airship and a helicopter.
I'm using dedicated heliblade spinners to make them hover. They work with ACBs and manual control but PID does nothing with them. I set the PID (General Purpose) to Altitude control and set the stimulus to 50 (and the other parameters) and the vehicle falls down. The dedicated heliblades don't move. Can the PID not use them? It says that it can control upwards facing propellers. Do dedicated heliblades not count as propellers? I know how to set up the PID but dediblades don't react to it. Am I doing something wrong?

It's possible to link AI to control imputs manually via ACBs, e.g. 'when [imput = move up] recieved, press [T]'. This works with AI and by extension with AI PIDs. I'm not sure whether it will work with GP PIDs, though.